Q139 / 150 · MHT CET 2021 (23 Sep Shift 2) · Physics
In common emitter amplifier, a change of $0.2 \mathrm{~mA}$ in the base current causes a change of $5 \mathrm{~mA}$ in the collector current. If input resistance is $2 \mathrm{k} \Omega$ and voltage gain is 75 , load resistance used in the circuit is
- A$8 \mathrm{k} \Omega$
- B$4 \mathrm{k} \Omega$
- C$12 \mathrm{k} \Omega$
- Correct answerD$6 \mathrm{k} \Omega$
Solution
$$
\beta=\frac{\Delta \mathrm{I}_{\mathrm{C}}}{\Delta \mathrm{I}_{\mathrm{b}}}=\frac{5}{0.2}=25
$$
Voltage gain, $A_v=\beta \frac{R_L}{R_i}$
$$
\therefore \mathrm{R}_{\mathrm{L}}=\frac{\mathrm{A}_{\mathrm{v}} \mathrm{R}_{\mathrm{i}}}{\beta}=\frac{75 \times 2}{25}=6 \mathrm{k} \Omega
$$
Hence, the correct answer is option: 'D'.